Over 400,000 total knee arthroplasties are performed each year in the United States to alleviate pain and disability associated with knee osteoarthritis. While total knee arthroplasty (TKA) reliably reduces pain and improves function in patients with knee osteoarthritis, recovery of quadriceps force to normal levels is rare. Walking performance remains about 20-30% lower than healthy age-matched older adults years after TKA, and more physically demanding tasks such as stair climbing are almost 50% lower. Within the past few years, less invasive TKA surgical techniques have emerged as promising alternatives to traditional TKA, possibly because of less surgical trauma to the quadriceps. Yet, no studies have specifically investigated the mechanisms by which less invasive TKA surgery might preserve quadriceps muscle function. The emergence of minimally invasive TKA surgery offers a unique opportunity to specifically investigate the impact of surgical trauma on the magnitude of quadriceps dysfunction and functional performance. The primary goal of this study is to determine if minimally invasive TKA improves quadriceps muscle force production and activation, increases knee range of motion, and decreases post-operative pain to improve functional outcomes compared to traditional TKA. The specific aims are 1) to determine if patients who undergo minimally invasive TKA have higher quadriceps muscle force and activation, greater knee range of motion and reduced post- operative pain compared to traditional TKA, and 2) to determine if functional performance (self-reports, 6 minute walk distance, get up and go time, functional stair climbing time) is higher in patients who undergo minimally invasive TKA compared to traditional TKA. Fifty patients (ages 50-85 years), who qualify for minimally invasive TKA will be randomized to receive either a traditional TKA or a minimally invasive TKA. Baseline testing will be performed before surgery and after surgery at 48hrs, 1, 3, 6 months and 1 year. This pilot study will asses the feasibility of a larger, randomized controlled clinical trial focusing on functional outcomes and the mechanisms accounting for potential improvements to provide evidence on which to base future clinical practice decisions for TKA. This study will also facilitate the design of more effective post-operative rehabilitation protocols targeting post-operative deficits. With a growing number of older adults requiring total knee arthroplasties each year, the consequences of quadriceps weakness and resulting disability after TKA present a growing health problem, which minimally invasive TKA surgery has the potential to mitigate. [unreadable] [unreadable] [unreadable]